在特定句子之间插入<span>标签，保留原始案例

Question

I need to insert a span tag between a certain text from a string, but it should be case insensitive and keep the original case.

$string ="This is what this is";

echo str_replace("this is","[span]this is[/span]",$string);

Returns:

This is what [span]this is[/span]

Expected:

[/span]This is[/span] what [span]this is[/span]

I know the str_replace is not the good option for that, and ir might be probably handled by Regex, but I have no idea in which direction I should go. Thanks in advance for your help!

Answer 1

Use preg_replace:

$string ="This is what this is";

echo preg_replace("/this is/i","[span]$0[/span]",$string);

Explanation:

/           : regex delimiter
   this is  : literally
/i          : regex delimiter, case insensitive

Replacement:

$0    : contains the whole match, ie "this is"