PHP Using str_replace along with preg_replace

问题

I have a string of comma separated values that comes from a database, which actually are image paths. Like so:

/images/us/US01021422717777-m.jpg,/images/us/US01021422717780-m.jpg,/images/us/US01021422717782-m.jpg,/images/us/US01021422718486-m.jpg

I then do like below, to split them at the , and convert them into paths for the web page.

preg_replace('~\s?([^\s,]+)\s?(?:,|$)~','<img class="gallery" src="$1">', $a)

Works well, but in one place further in my page, I need to change the -m to -l (which means large)

When I do like below (put a str_replace inside the preg_replace), nothing happens. How can I do something like this?

preg_replace('~\s?([^\s,]+)\s?(?:,|$)~','<img class="gallery" src="$1" data-slide="'.str_replace('-m','-l','$1').'">', $a)

回答1:

You're putting the str_replace() call in the output pattern for the preg_replace() call. That means preg_replace() is treating it as literal text.

What you want is something like this:

$imgtag = preg_replace(match, replacement, $a);
$imgtag = str_replace('-m','-l',$imgtag);

But, in my opinion it would be safer and easier to debug this stuff if you changed the order of your replacement operations, something like this:

foreach ($path in explode(",", $a)) {
  $path = str_replace('-m','-l',$path);
  $imgtag= sprintf ('<img class="gallery" src="%s">', $path);
  /* do something with the $imgtag */
}

That way you don't have to whistle into your modem :-) to program that regexp.

回答2:

Use str_replace on preg_replace return

$large = str_replace('-m','-l', preg_replace('~\s?([^\s,]+)\s?(?:,|$)~','<img class="gallery" src="$1">', $a));

Output will be

<img class="gallery" src="/images/us/US01021422717777-l.jpg">
<img class="gallery" src="/images/us/US01021422717780-l.jpg">
<img class="gallery" src="/images/us/US01021422717782-l.jpg">
<img class="gallery" src="/images/us/US01021422718486-l.jpg">

回答3:

Use preg_replace_callback():

preg_replace_callback(
    '~\s?([^\s,]+)\s?(?:,|$)~',
    function (array $matches) {
        $src   = $matches[1];               // this is "$1"
        $slide = str_replace('-m', '-l', $matches[1]);
        return '<img class="gallery" src="'.$src.'" data-slide="'.$slide.'">';
    },
    $a
);

Instead of the replace expression, preg_replace_callback() gets as its second argument a function that receives the list of matched expressions and returns the replacement string.

回答4:

Actually your str_replace is simply invoked before preg_replace is invoked. Result of str_replace is then passed as argument to preg_replace.

What I could suggest is using preg_replace_callback:

function replace_img($match)
{
  return '<img class="gallery" src="' .
    $match[1] .
    '" data-slide="' .
    str_replace('-m','-l',$match[1]) .
    '">';
}

preg_replace_callback('~\s?([^\s,]+)\s?(?:,|$)~','replace_img', $a);

回答5:

If you need two separate outputs from each comma-separated value, I would write a pattern that stores the fullstring match and the substrings on either side of the m in each file.

*note: I match the trailing - in the first capture group and the leading . in the second capture group for minimal assurance of accuracy. This is somewhat weak validation; you can firm it up if your project requires it by adding literal or more restrictive pattern components in the capture groups.

Code: (Demo)

$csv='/images/us/US01021422717777-m.jpg,/images/us/US01021422717780-m.jpg,/images/us/US01021422717782-m.jpg,/images/us/US01021422718486-m.jpg';
if(preg_match_all('~([^,]+-)m(\.[^,]+)~',$csv,$out,PREG_SET_ORDER)){
    foreach($out as $m){
        $mediums[]="<img class=\"gallery\" src=\"{$m[0]}\">";
        $larges[]="<img class=\"gallery\" src=\"{$m[0]}\" data-slide=\"{$m[1]}l{$m[2]}\">";
    }
}

var_export($mediums);
echo "\n\n";
var_export($larges);

Output:

array (
  0 => '<img class="gallery" src="/images/us/US01021422717777-m.jpg">',
  1 => '<img class="gallery" src="/images/us/US01021422717780-m.jpg">',
  2 => '<img class="gallery" src="/images/us/US01021422717782-m.jpg">',
  3 => '<img class="gallery" src="/images/us/US01021422718486-m.jpg">',
)

array (
  0 => '<img class="gallery" src="/images/us/US01021422717777-m.jpg" data-slide="/images/us/US01021422717777-l.jpg">',
  1 => '<img class="gallery" src="/images/us/US01021422717780-m.jpg" data-slide="/images/us/US01021422717780-l.jpg">',
  2 => '<img class="gallery" src="/images/us/US01021422717782-m.jpg" data-slide="/images/us/US01021422717782-l.jpg">',
  3 => '<img class="gallery" src="/images/us/US01021422718486-m.jpg" data-slide="/images/us/US01021422718486-l.jpg">',
)

来源：https://stackoverflow.com/questions/28254349/php-using-str-replace-along-with-preg-replace

标签

php

regex

preg-replace

filenames

image-file