How to use PHP regular expression function

PHP regular expression functions provide powerful text processing capabilities, including: preg_match: Check whether a matching pattern exists in a string. preg_match_all: Get an array of all matching patterns in the string. preg_replace: Replace all matching patterns in a string with replacement text. preg_split: Split the string into an array based on the matching pattern. Use modifiers: change the behavior of regular expressions, such as case insensitivity, multiline mode, etc.

How to use PHP regular expression function

Regular expression (regex) is a powerful pattern matching tool. Can be used to find, replace, or verify patterns in text. PHP provides a powerful regular expression function library to help developers process text data effectively.

preg_match: Check whether a matching pattern exists in the string.

<?php
$subject = "PHP is an open source programming language";
$pattern = "/PHP/";

if (preg_match($pattern, $subject)) {
    echo "匹配成功！";
} else {
    echo "匹配失败！";
}
?>

preg_match_all: Gets an array of all matching patterns in the string.

<?php
$subject = "PHP is an open source programming language";
$pattern = "/PHP/";

preg_match_all($pattern, $subject, $matches);

foreach ($matches[0] as $match) {
    echo $match . "\n";
}
?>

preg_replace: Replace all matching patterns in the string with replacement text.

<?php
$subject = "PHP is an open source programming language";
$pattern = "/PHP/";
$replacement = "Hypertext Preprocessor";

$new_subject = preg_replace($pattern, $replacement, $subject);

echo $new_subject; // 输出：Hypertext Preprocessor is an open source programming language
?>

preg_split: Split the string into an array based on the matching pattern.

<?php
$subject = "PHP, is, an, open, source, programming, language";
$pattern = "/,/";

$parts = preg_split($pattern, $subject);

foreach ($parts as $part) {
    echo $part . "\n";
}
?>

Use modifiers: Modifiers can change the behavior of regular expressions.

##iNo Case sensitivemMulti-line modesSingle-line modexAllow white space and commentseExecute PHP code

Modifier	Description

Practical Case: Verifying Email Address

<?php
$email = "example@example.com";
$pattern = "/^([a-zA-Z0-9_\-\.]+)@([a-zA-Z0-9_\-\.]+)\.([a-zA-Z]{2,5})$/";

if (preg_match($pattern, $email)) {
    echo "电子邮件地址有效！";
} else {
    echo "电子邮件地址无效！";
}
?>

The above is the detailed content of How to use PHP regular expression function. For more information, please follow other related articles on the PHP Chinese website!