Replacing array variables in string with preg_replace

Question

I am trying to use RegEx to replace an arrays value in a string that I have created.

For example:

$params = array(1 => 'butter', 2 => 'yellow', 3 => 'good', 4 => 'low-fat');
$query = 'type=$params[1]&color=$params[2]&taste=$params[3]&content=$params[4]';

I wanted to use preg_replace to replace all of the $params in the $query with the actual values for the string.

I had originally attempted:

$query = preg_replace("(\$params\[[1-9]+[0-9]*\])",$query,$params);

But that seemed to create an array for $query.

I was hoping to get:

$query =  'type=butter&color=yellow&taste=good&content=low-fat';

Any ideas where I am going wrong?

While the design is overall wrong, your preg_replace call has the parameters in the wrong order. The third parameter is the original string that you are manipulating. — kainaw
– kainaw, Commented Jun 26, 2015 at 19:25
To do a replacement for a key/value, I think you have to capture the key, and use it to reference the replacement value. \$params\[([1-9]+[0-9]*)\] — user557597
– user557597, Commented Jun 26, 2015 at 19:28

anubhava · Accepted Answer · 2015-06-26 19:32:00Z

2

You need to use preg_replace_callback for this:

$val = preg_replace_callback('/\$params\[(\d+)\]/', function ($m) use ($params)
      { return $params[$m[1]]; }, $query);
//=> type=butter&color=yellow&taste=good&content=low-fat

answered Jun 26, 2015 at 19:32

anubhava

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2 Comments

zeropsi Over a year ago

Thank you for this. Can you explain the difference between /\$params\[(\d+)\]/ and my original (\$params\[[1-9]+[0-9]*\])?

anubhava Over a year ago

You regex is capturing $params[1] where mine is just capturing 1. We just need number to get the indexed value from array params

iam-decoder · Accepted Answer · 2015-06-26 19:32:08Z

0

why not do something like this?

$params = array(
    'type' => 'butter',
    'color' => 'yellow',
    'taste' => 'good',
    'content' => 'low-fat'
);
$query = http_build_query($params);

answered Jun 26, 2015 at 19:32

iam-decoder

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1 Comment

zeropsi Over a year ago

I was attempting to use a predefined format in a string. I wanted to match the paramaters passed from the URL to that string, to create my variables.

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