CODEWITHSUNDEEP
phpregexpreg-replacepreg-match
Solomon Closson
Solomon Closson

Reputation: 6217

replace the following text with "" at the end of string

I have a variable that gets appended to a string early, but I need to replace it with an empty string if a condition is met (that condition can only be determined later on in the code).

For example:

$indent = str_repeat("\t", $depth);
$output .= "\n$indent<ul role=\"menu\">\n";

I now need to replace what gets appended to the $output string here with an empty string. This gets done elsewhere, but I still have access to the $indent variable, so I know how many "\t" has been added.

So, I know I can do it using preg_match and preg_replace like so:

if (preg_match("/\n$indent<ul role=\"menu\">\n$/", $output))
    $output = preg_replace("/\n$indent<ul role=\"menu\">\n$/", "", $output);
else
    $output .= "$indent</ul>\n";

But I am wondering on the performance here, and if there is a better way to do this? If someone can provide an example using my exact $output with newline and tab characters, that would be great.

Upvotes: 0

Views: 46

Answers (1)

BeetleJuice
BeetleJuice

Reputation: 40896

If you know the exact string, and you only want to remove it from the end of $output, using a regular expressions is really inefficient because it scans the whole string and parses it for regex rules.

Suppose we call the text you wish to crop $suffix. I would do:

//find length of whole output and of just the suffix
$suffix_len = strlen($suffix);
$output_len = strlen($output);

//Look at the substring at the end of ouput; compare it to suffix
if(substr($output,$output_len-$suffix_len) === $suffix){
    $output = substr($output,0,$output_len-$suffix_len); //crop
}

Live demo

Upvotes: 1

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