preg_match()

The function preg_match^[3] is the main regex search function^[4]. It returns a Boolean and asks the two mandatory parameters: the regex pattern and the string to scan.

The third parameter represents the variable which stores the results array.

Finally, the fourth accepts an PHP flag allowing to modify the function base behavior.

• Minimal example:

<?php
$string = 'PHP regex test for the English Wikibooks.';

if (preg_match('`.*Wikibooks.*`', $string)) {
    print('This texts talks about Wikibooks');
} else {
    print('This texts doesn\'t talk about Wikibooks');
}
?>

• Advanced example:

<?php
$string = 'PHP regex test for the English Wikibooks.';

if (preg_match('`.*Wikibooks.*`', $string), results, $flag) {
    var_dump(results);
} else {
    print('This texts doesn\'t talk about Wikibooks');
}
?>

Flag examples:^[5]

• PREG_OFFSET_CAPTURE: displays the searched substring position in the string.
• PREG_GREP_INVERT: displays the inverse in preg_grep().

preg_grep()

This function searches into arrays^[6].

preg_match_all()

To get all true results in one array, replace preg_match by preg_match_all^[7], and print by print_r.

Example to filter a file content:

$regex = "/\(([^)]*)\)/";
preg_match_all($regex, file_get_contents($filename), $matches);
print_r($matches);

preg_replace()

The function preg_replace accepts three parameters: the replaced and replacing string to treat.

<?php
// Replace spaces by underscores
$string = "PHP regex test for the English Wikibooks.";
$sortedString = preg_replace('`( )`', '_', $string);
echo $sortedString;
?>

preg_filter()

Same as preg_replace() but its result only include the replacements.

preg_split()

Decomposes a string.