Page 589 - Beginning PHP 5.3

Chapter 18: String Matching with Regular Expressions
To find all matches for a regular expression within a string, use the preg_match_all() function.
preg_match_all() takes the same parameters as preg_match() :

❑ The regular expression
❑ The string to search through
❑ An array to hold the matches (note that for preg_match_all() the array is not optional)

❑ Optional flags for the match operation
❑ An optional offset to start the search from
As with preg_match() , preg_match_all() returns the number of matches as an integer. Unlike
preg_match() , where this value can only be 0 or 1, preg_match_all() returns the total number of
matches in the string:

$text = “Call Mary on 499 012 3456, John on 876 543 2101, or Karen:
777 111 2345”;
echo preg_match_all( “/\b\d{3} \d{3} \d{4}\b/”, $text, $matches ); //

Displays “3”
preg_match_all() stores all matches in the array passed to it as the third argument. The matches are
stored in the first element of the array (with an index of zero), as a nested array:
$scores = “John: 143 points, Anna: 175 points, and Nicole: 119 points”;
preg_match_all( “/\w+\:\s\d+ points/”, $scores, $matches );
echo $matches[0][0] . “ < br / > ”; // Displays “John: 143 points”
echo $matches[0][1] . “ < br / > ”; // Displays “Anna: 175 points”

echo $matches[0][2] . “ < br / > ”; // Displays “Nicole: 119 points”
If your expression contains subpatterns, the text matches from these subpatterns are stored in
subsequent array elements. Consider the following example:
$scores = “John: 143 points, Anna: 175 points, and Nicole: 119 points”;
preg_match_all( “/(\w+)\:\s(\d+) points/”, $scores, $matches );
echo $matches[0][0] . “ < br / > ”; // Displays “John: 143 points”
echo $matches[0][1] . “ < br / > ”; // Displays “Anna: 175 points”
echo $matches[0][2] . “ < br / > ”; // Displays “Nicole: 119 points”

// The following code displays:
//
// John scored 143
// Anna scored 175
// Nicole scored 119

echo $matches[1][0] . “ scored “ . $matches[2][0] . “ < br / > ”;
echo $matches[1][1] . “ scored “ . $matches[2][1] . “ < br / > ”;

echo $matches[1][2] . “ scored “ . $matches[2][2] . “ < br / > ”;
As you can see from this example, the element with index 1 is a nested array containing all the
matches from the first subpattern (the players ’ names), and the element with index 2 contains all
the matches from the second subpattern (the scores). For each subpattern in the expression, an extra
element is created in the matches array.

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