Use preg_quote() function in PHP to escape regex patterns before it is applied in run time. The preg_quote() function puts a backslash in front of every character within the specified string that would be a part of the regex syntax in PHP, thereby making them escape sequences. These characters include:
. \ + * ? [ ^ ] $ ( ) { } = ! | : – #
Syntax:
string preg_quote( string $str, string $delimiter = NULL )
Parameters:
- $str: This parameter holds the input string.
- $delimiter: It is optional parameter. The most common delimiter is ‘/’ as it is not a special regex character that would be normally handled by preg_quote(). Primarily used in conjunction with preg_replace() function.
Returns: It returns the delimiter containing string.
Below programs illustrates the preg_quote() function.
Program 1:
<?php // Create a string which need to be escaped $str = "Welcome to GfG! (+ The course fee. $400) /"; echo "Before Processing - " . $str . PHP_EOL; // Use preg_quote() on above string $processedStr = preg_quote($str); // Display the output echo "After Processing - " . $processedStr; ?> |
Before Processing - Welcome to GfG! (+ The course fee. $400) / After Processing - Welcome to GfG\! \(\+ The course fee\. \$400\) /
Notice that a backslash was put in front of every special character, but not for the forward slash. For that, we can use the delimiter, see the program below:
Program 2
<?php // Create a string which need to be escaped $str = "Welcome to GfG! (+ The course fee. $400) /"; echo "Before Processing - " . $str . PHP_EOL; // Use preg_quote() on above string $processedString = preg_quote($str, '/'); // Display the output echo "After Processing - " . $processedString; ?> |
Before Processing - Welcome to GfG! (+ The course fee. $400) / After Processing - Welcome to GfG\! \(\+ The course fee\. \$400\) \/
Below program demonstrates the combined use of preg_quote() and preg_replace() function.
Program 3:
<?php // PHP Program emphasize the word within * * and // use font style to italic within [ ] using // both preg_quote() and preg_replace() function $str = "The *article* was written by [GFG]"; // The words to be formatted $word1 = "*article*"; $word2 = "[GFG]"; // The first string only applies bold to word 1, // preg_quote() escapes the * * $processedStr1 = preg_replace("/" . preg_quote($word1, '/') . "/", "<strong>" . $word1 . "</strong>", $str); echo "BOLD ONLY - " . $processedStr1 . PHP_EOL; // The second string only applies italics to // word 2, preg_quote() escapes the [ ] $processedStr2 = preg_replace("/" . preg_quote($word2, '/') . "/", "<em>" . $word2 . "</em>", $str); echo "ITALIC ONLY - " . $processedStr2 . PHP_EOL; // Combining both text formattings and display $bothReplacementsCombined = preg_replace("/" . preg_quote($word2, '/') . "/", "<em>" . $word2 . "</em>", $processedStr1); echo "BOTH COMBINED - " . $bothReplacementsCombined; ?> |
BOLD ONLY - The *article* was written by [GFG] ITALIC ONLY - The *article* was written by [GFG] BOTH COMBINED - The *article* was written by [GFG]
Note: To notice the application of the text formatting tags, you should run PHP on your local server and echo to the browser.
