How do I replace custom "tags" in a string?

Given the following:

$foo = "Yo [user Cobb] I heard you like dreams so I put a dream in yo dream in yo dream so you can dream while you dream while you dream."

I'd like to do this:

$foo = bar($foo);

echo $foo;

And get something like this:

Yo Cobb I heard you like dreams so I put a dream in yo dream in yo dream so you can dream while you dream while you dream.

I'm unsure of how the bar function should work. I think this is doable with regular expressions but I personally find those hard to understand. Using the strpos function is another method but I wonder if there is a better solution.

开发者_如何学C

Pseudocode is fine but actual code will be appreciated.

Edit:

These tags are not placeholders as the 2nd part is a variable value.

Edit:

All of the str_replace answers are incorrect as the tags contain variable content.

---

You could use preg_match_all to search the string for tags.

function bar($foo)
{
    $count = preg_match_all("/\[(\w+?)\s(\w+?)\]/", $foo, $matches);
    if($count > 0)
    {
         for($i = 0; $i < $count; $i++)
         {
             // $matches[0][$i] contains the entire matched string
             // $matches[1][$i] contains the first portion (ex: user)
             // $matches[2][$i] contains the second portion (ex: Cobb)

             switch($matches[1][$i])
             {
                 case 'user':
                     $replacement = tag_user($matches[2][$i]);
                     str_replace($matches[0][$i], $replacement, $foo);
                     break;
             }
         }
    }
}

Now you can add more functionality by adding more cases to the switch.

---

As the tags contain content you want to parse and are not static to be replaced tags you’ll have to use regular expressions. (It’s the easiest way to go.)

preg_replace() is the regular expression function to replace text.

$pattern = '/\[user (\w+)\]/i';
$rpl     = '<a href="http://example.com/user/${1}">${1}</a>';
return preg_replace($pattern, $rpl, $foo);

This will match for a [user xy] tag where xy is a word (sequence of word-characters) of at least one character. As it is in parenthesis it is accessible with {1} in the replace-string. $foo is the string you want to parse. Returned is the parsed string with replaced tag. The i modifier on the pattern will make the matching case-insensitive. Remove it if you want it to be case-sensitive.

(The example you gave parses from [user Cobb] to a wikipedia url leonardo dicabrio, which is in no correspondence to neither user nor Cobb. So however you got there, you’ll have to do that (query a db? whatever). If it was just not careful enough providing example code; you probably wanted to point to a static url and add part of the tag content to it, which is what I did here.)

---

str_replace() is going to be your best option:

function bar($foo) {
   $user = 'Cobb';
   return str_replace('[user]', $user, $foo);
}

$foo = 'Yo [user] I heard you like dreams so I put a dream in yo dream in yo dream so you can dream while you dream while you dream.'
$foo = bar($foo);
print $foo; // Will print "Yo Cobb I heard you like dreams so I put a dream in yo dream in yo dream so you can dream while you dream while you dream."

---

What about str_replace?

function bar(foo)
return str_replace($arrayWithStringsToGetReplaced,
                   $arrayWithStringsToReplaceWith,
                   $foo)

If I understand the comments below correctly.

This is obviously beyond me. Moving on... :)

---

Regular Expressions are the way to go. Hard yes, but the benefit gained from learning them far outweighs the effort needed to learn.

From php.net

<?php
$text = 'The price is PRICE ';

$lookFor = 'PRICE';
$replacement = '$100';

echo $replacement.'<br />';
//will display
//$100


echo str_replace($lookFor, $replacement, $text).'<br />';
//Will display
//The price is $100
?>