Replacement content with PHP variables without double quotes or curly braces

M66 2025-05-31

In PHP development, string replacement is a common requirement. Especially in multilingual or multi-byte characters, the mb_eregi_replace function becomes a very practical tool because of its good support for multi-byte characters and case-insensitive matching.

This article will explain how to use the mb_eregi_replace function to deal with PHP variables in strings but not double quotes or curly braces. And demonstrate how to use variables safely in replacement operations.

Background description

In PHP, variable parsing usually occurs in double quoted strings or curly braces, for example:

 echo "Hello $name";      // Variables will be parsed
echo "Hello {$name}";    // Variables will also be parsed

But if the string is not enclosed in double quotes, or the variable is not wrapped in curly braces, the parsing will not take effect:

 echo 'Hello $name';      // Output：Hello $name（Variable not parsed）
echo 'Hello '.$name;     // correct，Variables are parsed as splicing

When replacing this with mb_eregi_replace , if a variable appears in the replacement template and is not processed correctly, it may cause the variable name to be treated as a normal string or the matching result is incorrect.

Introduction to mb_eregi_replace function

mb_eregi_replace is a function that supports regular case-insensitive replacement in PHP's multibyte string function family. The function definition is as follows:

 string mb_eregi_replace ( string $pattern , string $replacement , string $string [, string $option = "msr" ] )

$pattern : Regular expression pattern, case-insensitive.
$replacement : Replaced string, which can contain variables.
$string : target string.
$option : Match option, default "msr" .

Key question: How to use variables in replacement?

Suppose you want to replace the $varName variable in the string to its actual value, but the original string does not wrap the variable with double quotes or curly braces, such as:

 $content = "This is a variable$varNameTest";

If you want to replace $varName with mb_eregi_replace as a specific value, such as "m66.net" , write directly:

 $replacement = "m66.net";
mb_eregi_replace('\$varName', $replacement, $content);

Here \$varName is the literal $varName in the regular expression, replaced by m66.net . Note that $ needs to be escaped in the regularity.

Sample code demonstration

 <?php
// Target string，Variable not wrapped in double quotes
$content = 'Visit our site：$siteName，Experience more exciting content！';

// The variable name that needs to be replaced（Literal）
$pattern = '\$siteName';

// The actual value of the replacement
$replacement = 'm66.net';

// usemb_eregi_replaceMake a replacement，Ignore case
$newContent = mb_eregi_replace($pattern, $replacement, $content);

// Output替换结果
echo $newContent;
?>

Output result:

 Visit our site：m66.net，Experience more exciting content！

Details

Regular escape : Since you want to match the $ symbol in the string, you must write \$ in the regular expression.
Variable replacement : The replacement string can be any value or can be passed in a dynamically.
Scenarios without double quotes or curly braces : directly match literal variable names to avoid mismatch.
Multi-byte support : mb_eregi_replace perfectly supports UTF-8 and other encodings, suitable for Chinese replacement needs.

in conclusion

When the target string contains unparsed PHP variables (such as $var without double quotes or curly braces), mb_eregi_replace can be replaced by matching the literal variable name.
Pay attention to the escape of regular expressions, especially the $ symbol when using them.
The replacement content can be replaced directly with variables to ensure dynamic flexibility.
mb_eregi_replace is suitable for case-insensitive replacement in multi-byte environments.

mb_eregi_replace