PHP and MySQL by Example- P7

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Example 8.36. Random Array of Two Strings
Figure 8.43. Selecting two random elements from an array. Output from Example 8.36. Figure 8.44. Refreshing the screen for two more random elements. Shuffling a Numeric Array (Randomizing the Values) The shuffle() function causes the elements of a numerically indexed array to be randomized. It randomizes the values of an associative array, but destroys the keys. The function returns boolean TRUE or FALSE. See Example 8.37. Prior to PHP 4.2.0, it was necessary to seed the random number generator (give it a different starting point) with srand(), but now that is done automatically. To randomize a selected number of elements of an array, see the array_rand() function. Format boolean_value = shuffle( array_name ); Example: $numbers = ( 1, 2, 3, 4, 5, 6, 7, 8, 9, 10); shuffle($numbers); Output: 9 4 6 5 1 3 2 8 7 10 Example 8.37. Shuffle the Array Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Shuffle the Array Explanation 1 An array called $months is created. A range of 1 to 12 months is created with the range() function. 2 It is no longer necessary to seed the random number generator with srand(); that is, give it a random starting point. 3 The shuffle() function shuffles or randomizes the elements of the array, $months. See Figure 8.45 for before and after the shuffle. Figure 8.45. Shuffling an array of months. Output from Example 8.37. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
8.2. Modifying Arrays (Unsetting, Deleting, Adding, and Changing Elements) PHP makes it easy to modify both numeric and associative arrays by providing a number of built-in functions to add new elements, remove existing elements and/or replace those elements with new ones, copy elements from one array to another, to rearrange elements, and so on. 8.2.1. Removing an Array and Its Elements There are a number of built-in functions to remove elements from an array (see Table 8.8). Table 8.8. Functions That Remove Elements Function What It Does array_pop() Removes and returns the last element of an array array_shift() Removes and returns the first element of an array array_splice() Removes and/or replaces elements in an array array_unique() Removes duplicates from an array Removing an Entire Array The unset() function completely removes an array, as though it never existed. Setting the element’s value to zero or the null string assumes the element is still there. Format void unset ( mixed var [, mixed var [, mixed ...]] ) Example: $colors=array("red","green","blue"); unset($colors); // Removes the array Removing the Last Element of an Array The array_pop() function removes the last elment of an array and returns it, shortening the array by one element. If the array is empty (or is not an array), NULL will be returned. This function resets the array pointer after it is used. Format mixed array_pop ( array &array ) Example: $animals = ("dog", "cat", "pig", "cow"); $strayed = array_pop($animals); // The "cow" is removed from the // array, and assigned to $strayed Example 8.38. array_pop()
3 $popped = array_pop($names); // Remove last element echo "After pop(): "; 4 foreach($names as $val){ echo "$val "; } echo "$popped was removed from the end of the array."; ?> Explanation 1 The numeric array $names is created and assigned a list of values. 2 The foreach loop is used to iterate through the array and display its values. 3 The array_pop() function removes the last element of the array, "Jerry". The popped off value is returned and assigned to a variable, called $popped. 4 The $names array is displayed after the last element was removed with the array_pop() function. See Figure 8.46. Figure 8.46. The last element from an array is removed with pop(). Output from Example 8.38. Removing the First Element of an Array The array_shift() function removes the first element from an array and returns it, decreasing the size of the array by one element. All numerical array keys start at zero and literal keys will not be touched. If an array is empty (or is not an array), NULL will be returned. See Example 8.39. Format mixed array_shift ( array &array ) Example: $colors=array("red", "blue","green", "yellow"); // First element, "red", removed Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
and assigned to $shifted_off_color $shifted_off_color = array_shift( $colors); Example 8.39. array_shift() Explanation 1 A numeric array called $names is defined. 2 The foreach loop is used to iterate through the array and get the individual values, each one in turn, assigned to $val. 3 The array_shift() function removes and returns the first element of the array, "Tom", assigned to $shifted. 4 The foreach loop is used again to iterate through the array showing that the array has been shortened by one element. See Figure 8.47. 5 The value returned from the array_shift() function is "Tom", the first element in the array. This value is printed. See Figure 8.47. Figure 8.47. Removing the first element of an array with shift(). Output from Example 8.39. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Removing Duplicate Values from an Array The array_unique() function removes duplicate values from an array and returns a new array without the duplicates. The array_unique() function first sorts the values treated as strings, then keeps the first key encountered for every value, and thereafter, ignores any duplicate keys. Two elements are considered equal only if they are identical (same data type, same value); that is, the === operator applies. See Example 8.40. Format array array_unique ( array array ) Example: unique_values = array_unique(array("apples", "pears", "apples", "Apples")); // Removes duplicates and returns an array with unique values. Example 8.40. array_unique() Explanation 1 A numerically indexed array called $numbers is assigned a list of integers. 2 The foreach loop is used to loop through the array, $numbers. The value of each of the elements is printed. 3 Notice that there are a number of duplicate values in the array $numbers. The array_unique function returns an array with duplicates removed; that is, an array of unique values. See Figure 8.48. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Figure 8.48. The array_unique() function. Output from Example 8.40. 8.2.2. Adding Elements to an Array PHP provides built-in functions to increase the size of an array by allowing you to add elements.(see Table 8.9). Table 8.9. Array Functions to Add Elements to an Array Function What It Does array_push() Pushes a new element(s) onto the end of the array array_splice() Removes and/or adds elements to an array at any position array_unshift() Adds a new element(s) to the beginning of the array Adding Elements to the Beginning of an Array The array_unshift() function prepends one or more elements onto the beginning of an array, increasing the size of the array by the number of elements that were added. It returns the number of elements that were added. See Example 8.41. Format int array_unshift ( array &array, mixed var [, mixed ...] ) Example: $colors=("yellow", "blue", "white"); $added=array_unshift($colors,"red","green"); // "red", "green", "yellow", "blue", "white" Example 8.41. array_unshift()
2 foreach($names as $val){ echo "$val "; } // Add new element to the beginning 3 array_unshift($names, "Willie", "Liz"); echo "After unshift(): "; foreach($names as $val){ echo "$val "; } 4 echo "Willie and Liz were added to the beginning of the array."; ?> Explanation 1 The numeric array called $names is assigned five string values. 2 The foreach loop is used to iterate through the array $names. Each value is printed as the loop cycles through the array. 3 The array_unshift() function is used to append new elements to the beginning of an array. In this example, "Willie" and "Liz" are prepended to the array $names. "Willie" will be assigned the index of 0, and all the rest of the index values will be incremented accordingly. 4 Figure 8.49 displays the array after "Willie" and "Liz" are prepended with the array_unshift() function. Figure 8.49. Adding elements to the beginning of an array with unshift(). Output from Example 8.41. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Adding Elements to the End of an Array The array_push() function pushes one or more elements onto the end of array, increasing the size of the array by the number of elements that were added. It returns the number of elements that were added. See Example 8.42. Format int array_push ( array &array, mixed var [, mixed ...] ) Example: $colors=("yellow", "blue", "white"); $added = array_push($colors, "red", "green"); // "yellow", "blue", "white", "red", "green" Example 8.42. array push() Explanation 1 The numeric array called $names is assigned four string values. 2 The foreach loop is used to iterate through the array $names. Each value is printed as the loop cycles through the array. 3 The array_push() function is used to append new elements to the end of an array. In this example, "Tina" and "Donna" are appended to the array $names. "Tom" will be assigned the index of 0, and all the rest of the index values are incremented accordingly. 4 Figure 8.50 displays the array after "Tina" and "Donna" are appended to it with the array_push() function. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Figure 8.50. The array_push() function. Output from Example 8.42. Splicing an Array—Removing and Adding Elements The word splice is often associated with splicing two pieces of rope, film, or DNA strands. It means to join. Array elements can be removed and then what is left can be joined back together. The array_splice() function removes a portion of the array and joins it back together, possibly replacing the removed values with new ones. The first argument is the array, and the second argument is the place in the array (called the offset) where you want the function to start removing elements. Offset 0 is the first position in the array. If you are taking elements from the end of the array, the offset starts at a negative number. An offset of –1 indicates the end of the array. The third, optional argument tells the function how many elements you want to remove. If you do not specify a length, splice() removes everything from the offset to the end of the array. A fourth optional argument allows you to list the replacement values. (Use the built-in count() function to get the length of the array.) The returned values are the elements that were removed. Simply put, splice() removes any number of elements from an array, starting at some position, and lets you replace those elements with new ones if you want to. The next set of examples demonstrate how array_splice() is used to remove and replace elements in an array. Figure 8.51 displays the resulting spliced array. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Figure 8.51. The splice() function. Each numbered example is applied to the original array. Format array array_splice ( array &input, int offset [, int length [, array replacement]] ) Examples: 1. $foods=array("bread","milk", "eggs", "fruit", "meat"); array_splice($foods, 4); // Removes "meat" 2. $foods=array("bread","milk", "eggs", "fruit", "meat"); array_splice($foods,0,3); // Removes "bread", "milk", and "eggs" 3. $foods=array("bread","milk", "eggs", "fruit", "meat"); array_splice($foods, -2); // Removes "fruit" and "meat" 4. $foods=array("bread","milk", "eggs", "fruit", "meat"); array_splice($foods, 0,0, array("fish", "cheese")); // Prepends the array with "fish" and "cheese" 5. $foods=array("bread","milk", "eggs", "fruit", "meat"); array_splice($foods, -3, 2, "veggies"); // Backs up three from the end, removes "eggs" and "fruit", // and replaces them with "veggies" 6. $foods=array("bread","milk", "eggs", "fruit", "meat"); array_splice($foods,2 ,count($foods),array("beer","peanuts")); // Removes "eggs", "fruit", and "meat" and replaces them with // "beer" and "peanuts" Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
8.2.3. Copying Elements of an Array The array_slice() Function In case you get the terms splice and slice confused, think of a splice as joining two pieces of tape or rope together and think of slice as in a slice of bread or a slice of apple pie. The array_slice() function extracts a slice (some specified elements) of an array, specified by an offset and the number of elements to extract. It returns the specified sequence of elements from the array and resets the key/index values. If the boolean argument is set to TRUE, then the index values will not be adjusted. To simplify, the array_slice() function copies elements from one array, and assigns them to another array. The array that is being sliced is not changed. See Example 8.43 Format array array_slice ( array array, int offset [, int length [, bool preserve_keys]] ) array = array_slice ( array_name, integer offset); array = array_slice ( array_name, integer offset, length); array = array_slice ( array_name, integer offset, length, boolean value); Example: foods = array("bread", "milk", "eggs", "fruit"); $slice = array_slice ( $foods, 2); // $slice contains "eggs" $slice = array_slice ( $foods, 0, 2); // $slice contains "bread" and "milk" $slice = array_slice ( $foods, -2, 1); // $slice contains "milk" $slice = array_slice ( $foods, 0, 3, TRUE); // $slice contains "bread", "milk", and "eggs"; the order of the // keys/index values are preserved Example 8.43. Code View: array_slice() Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Explanation 1 $names is a numeric array intialized with a list of strings. 2 The first argument to the array_slice() function is the offset position, where to start selecting elements, and the second argument is the length or number of elements to copy. In this example, "Tom", "Dan", and "Steve" are copied into an array called $good_guys. 3 In this example, the offset starts from the end of the array. An offset of –2 means back up two positions from the end of the array. Because a length is not specified, the array_splice() function will copy the last two elements, "Christian" and "Jerry", from the array and assign them to $good_guys. 4 For output of this example, see Figure 8.52. Figure 8.52. The array_slice() function. Output from Example 8.43. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
8.2.4. Combining and Merging Arrays The array_combine() Function The array_combine() function returns an array made up of keys and values. The keys of the new array are the made up of the values from the first array and the values associated with the new keys are made up of the values from the second array (PHP 5). The function returns FALSE if there are an unequal number of values in either of the arrays used as arguments. Format array array_combine ( array keys, array values ) Example: $titles=array("President", "Programmer", "Accountant"); $names=array("Bill McClintock", "Pearl White", "Barry Buck"); $new_array = array_combine( $titles, $names); // Returns: "President =>"Bill McClintock, "Programmer"=>"Pearl // White", "Accountant"=>"Barry Buck" Example 8.44. Combining Arrays Combining Arrays Explanation 1 An numeric array called $abbrev is assigned three string values. 2 An numeric array called $states is assigned three string values. 3 The array_combine() function combines the two arrays so that the values in the first array $abbrev become the keys corresponding to the values in the second array, $states. A new array called $combined, an associative array of key–value pairs, is returned. 4 The combined array is printed. The keys are made up of the first array, $abbrev, and the values from the second array, $states. See Figure 8.53 for the output. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Figure 8.53. Combining arrays with keys and values. Output from Example 8.44. The array_merge() Function The array_merge() function joins two or more arrays together to return a single array. The values of one array are appended to the end of the previous array. Format array array_merge ( array array1 [, array array2 [, array ...]] ) Example: $newarray=array_merge($array1, $array2); // Returns one array If array elements have the same keys, then the key of the first array will be overwritten by the key of the next one. If, however, the arrays contain numeric keys, the later value will not overwrite the original value, but will be appended. If only one array is given and the array is numerically indexed, the keys get reindexed in order. Merging Numerically Indexed Arrays Example 8.45 demonstrates the merging of numerically indexed arrays using the array_merge() function. Example 8.45. Merging Arrays Merging Arrays
Explanation 1 A numeric array, called $primary, is initialized. 2 A second numeric array, called $secondary, is initialized with three values. 3 The array_merge() function appends the second array to the first one. The index values of the second array are incremented in the order in which they appear in the new merged array. 4 The merged arrays are shown in Figure 8.54. Figure 8.54. Merging two arrays. Output from Example 8.45. Merging Associative Arrays Example 8.46 demonstrates merging associative arrays and removing duplicate keys. Example 8.46. Merging Associative Arrays
1 $cyclewear1=array('item'=>'jersey', 'color'=>'blue', 'type'=> 'hooded'); 2 $cyclewear2=array('size'=>'large','color'=>'white', 'cost'=>'145'); echo 'After merging $cyclewear1 and $cyclewear2',""; 3 $merged=array_merge($cyclewear1, $cyclewear2); 4 print_r($merged); ?> Explanation 1 An associative array is initialized with key–value pairs. 2 This associative array has a 'color' key, and so does the first one. When they are merged, the value of the 'color' key in the first array will be overwritten by the value in the second array. 3 The second array, $cyclewear2, is appended to the first array, $cyclewear1. If the first array and the second array have duplicate keys, the duplicate keys in the first array are overwritten. 4 The output is printed as shown in Figure 8.55. Figure 8.55. Merging associative arrays. Output from Example 8.46. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
The array_merge_recursive() Function The array_merge_recursive() function merges two or more arrays recursively. array_merge_recursive() merges the elements of one or more arrays together so that the values of one are appended to the end of the previous one. It returns the resulting array. Format array array_merge_recursive ( array array1 [, array ...] ) If you have two associative arrays being merged and their keys are the same but their values are different, the array_merge_recursive() function will combine the values of both arrays into another array as shown in Example 8.47. If the arrays have the same numeric key, the later value will not overwrite the original value, but it will be appended. Example 8.47. Merging Associative Arrays Merging Associative Arrays Explanation 1 The associative array, $cyclewear1, contains key–value pairs describing an item called "jersey". 2 The associative array, $cyclewear2, contains more descriptive key–value pairs, and also has a 'color' key, but with a different value. 3 The array_merge_recursive() function merges the two arrays and where the key is the same, creates an array of values. The 'color' key now consists of an array of colors, 'blue' and 'white'. 4 After merging two arrays recursively, the new array returned from array_merge_recursive() is printed. See Figure 8.56. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Figure 8.56. Merging keys and values. Output from Example 8.47. 8.2.5. Array Operators The array operators used to manipulate arrays are listed in Table 8.10. These are the same operators we discussed in Chapter 5, “Operators,” but they are now applied to arrays rather than strings and numbers. Table 8.10. Array Operators Operator Function Meaning $a + $b Union Union of $a and $b $a == $b Equality TRUE if $a and $b have the same key–value pairs $a === Identity TRUE if $a and $b have the same key–value pairs in the same order $b and of the same types $a != $b Inequality TRUE if $a is not equal to $b $a $b Inequality TRUE if $a is not equal to $b $a !== Nonidentity TRUE if $a is not identical to $b $b Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.