How to intercept string using regular expression in PHP

In PHP programming, sometimes you need to intercept part of a string, but you don't know the specific location. In this case, you need to use regular expressions to extract the target text.

Regular expression is a powerful text matching tool that can match specific patterns in text through some metacharacters, thereby enabling text search, replacement, interception and other operations.

In PHP, the steps to use regular expressions to intercept strings are as follows:

1. Use the preg_match() function to match the target text
   preg_match() function is commonly used for strings One of the matching functions, its syntax is as follows:

preg_match($pattern, $string, $matches);

Among them, $pattern represents the regular expression pattern and $string represents Target text, $matches represents the matching result output array.

Sample code:

$text = "Today is September 1, 2019";
$pattern = "/d{4}-d{2}-d{2 }/";
preg_match($pattern, $text, $matches);
print_r($matches);

Output result:

Array
(

[0] => 2019-09-01

)

In the above code, the regular expression pattern "/d{4}-d{2}-d{2}/" means matching date characters in the yyyy-mm-dd format String, through the preg_match() function, the string matching the pattern in the target text can be extracted and saved into the $matches array.

2. Use the preg_replace() function to replace the target text
   In addition to using the preg_match() function to extract the target text, you can also use the preg_replace() function to replace the string in the target text that matches the regular expression pattern Replaced with the specified string.

The syntax of the preg_replace() function is as follows:

preg_replace($pattern, $replace, $string);

where $pattern represents the regular expression pattern , $replace represents the string to be replaced, and $string represents the target text.

Sample code:

$text = "This is a text that needs to be replaced";
$pattern = "/need/";
$replace = "Courage";
$text_new = preg_replace($pattern, $replace, $text);
echo $text_new;

Output result:

This is a text that dares to be replaced

In the above code, the regular expression pattern "/need/" means matching the "need" string. Use the preg_replace() function to replace all strings that match the pattern in the target text with the "brave" string, and get The new text after replacement.

3. Use the preg_split() function to split the target text
   In addition to using the preg_match() function and preg_replace() function, you can also use the preg_split() function to split the target text into multiple parts according to the regular expression pattern. substring.

The syntax of the preg_split() function is as follows:

preg_split($pattern, $string);

Among them, $pattern represents the regular expression pattern, $string Represents the target text.

Sample code:

$text = "a,b,c,d,e";
$pattern = "/,/";
$array = preg_split( $pattern, $text);
print_r($array);

Output result:

Array
(

[0] => a
[1] => b
[2] => c
[3] => d
[4] => e

)

In the above code, the regular expression pattern "/,/" means matching comma characters. Use the preg_split() function to use all characters that match the pattern in the target text as delimiters, split the target text into multiple substrings, and save them to Array $array.

In summary, using regular expressions to intercept strings in PHP can be achieved through the preg_match() function, preg_replace() function and preg_split() function. In specific practice, you need to choose appropriate functions according to different needs, and through learning and practice, master the skills of using regular expressions in order to perform string operations more efficiently.

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