Match any horizontal whitespace characters at the start of each line in multiline strings in PHP

Question

I want to replace all empty spaces on the beginning of all new lines. I have two regex replacements:

$txt = preg_replace(\"/^　+/m\", \'\', $txt);
$txt = preg_rep         


        

Answer 1

Since you want to remove any horizontal whitespace from a Unicode string you need to use

• \h regex escape ("any horizontal whitespace character (since PHP 5.2.4)")
• u modifier (see Pattern Modifiers)

Use

$txt = preg_replace("/^\h+/mu", '', $txt);

Details

• ^ - start of a line (m modifier makes ^ match all line start positions, not just string start position)
• \h+ - one or more horizontal whitespaces
• u modifier will make sure the Unicode text is treated as a sequence of Unicode code points, not just code units, and will make all regex escapes in the pattern Unicode aware.