使用PHP preg_match的多行字符串的正则表达式

Question

I'm trying to build a pattern for a multiline string, that must start with <?php or whitespace + <?php and NOT end with ?> or ?> + whitespace.

My attempt was /^\s?<\?php.*[^>]\s?$/s but it did not work. Also tried the negative lookahead - no use.

Any idea? Thanks in advance.

Answer 1

You can use

(?s)^\s*<\?php(?!.*\?>\s*$).*+$

See demo

Regex explanation:

• (?s) - Enable singleline mode for the whole pattern for . to match newline
• ^ - Start of string
• \s* - Optional whitespace, 0 or more repetitions
• <\?php - Literal <?php
• (?!.*\?>\s*$) - Look-ahead checking if the string does not end with ?>whitespace
• .*+$ - Matches without backtracking any characters up to the string end.

The possessive quantifier (as in .*+) enables us to consume characters once, in 1 go, and never come back in search of possible permutations.

Possessive quantifiers are a way to prevent the regex engine from trying all permutations. This is primarily useful for performance reasons.

And we do not to use explicit SKIP-FAIL verbs then.