November 6, 2012

How to dynamically create a string in PHP?

Question by All

I have a predefined pattern for building a string, which should be created regularly throughout the script.

$str="$first - $second @@ $third"; // pattern for building the string
$string= ..?? // string should be built here based on the pattern

Currently, I am using eval to generate the string in place based on the pattern originally defined. However, as this happens occasionally and eval is generally bad, I wish to find another method.

NOTE that the pattern is defined only one time above all codes, and I can edit the pattern of all the script by one line only. Thus, what makes $string should not be touched for any change.

I tried create_function, but needs the same number of arguments. With eval, I can easily change the pattern, but with create-function, I need to change the entire script. For example, if changing the string pattern to

$str="$first @@ $second"; // One arg/var is dropped

eval Example:

$str="$first - $second @@ $third"; // Pattern is defined one-time before codes
eval("$string = "$str";");

create_function Example:

$str=create_function('$first,$second,$third', 'return "$first - $second @@ $third";');

Answer by Vulcan

You can use the string formatting capabilities offered by sprintf or vsprintf.

$format = "%s - %s @@ %s"; // pattern for building the string
$first = "word1";
$second = "word2";
$third = "word3";
$string = sprintf($format, $first, $second, $third);

You can use vsprintf if you wish to pass an array.

$format = "%s - %s @@ %s"; // pattern for building the string
$values = array($first, $second, $third);
$string = vsprintf($format, $values);

Answer by Starx

Seems to be rather simple thing to me. Use str_replace() and replace based on patterns

$str="$first$ - $second$ @@ $third$"; // pattern for building the string

$newstr = str_replace('$first$', $first, $str);
$newstr = str_replace('$second$', $second, $newstr);
$newstr = str_replace('$third$', $third, $newstr);

Author: Nabin Nepal (Starx)

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