How to replace the first occurrence in a string? - php

Question

I am trying to replace every question mark "?" in a string with a values in an array.
I need to go through a string, and replace the first occurrence of '?' in the string with a value. I would need to do that for every occurrence
Here is what I tried
function sprintf2($str='', array $values = array(), $char = '?')
{
if (!$str){
return '';
}
if (count($values) > 0)
{
foreach ($values as $value)
{
$str = preg_replace('/'. $char . '/', $value, $str, 1);
}
}
echo $str;
}
But I am getting the following exception
preg_replace(): Compilation failed: nothing to repeat at offset 0
The following shows how I am calling the function
$bindings = array(10, 500);
$str = "select * from `survey_interviews` where `survey_id` = ? and `call_id` = ? limit 1";
sprintf2($str, $bindings);
What am I doing wrong here? why do I get this exception?

Answer 1

Use str_replace instead of preg_replace, since you're replacing a literal string, not a regular expression pattern.
However, str_replace always replaces all matches, there's no way to limit it to just the first match (preg_replace is similar). The 4th argument is not a limit, it's a variable that gets set to the number of matches that were found and replaced. To replace just one match, you can combine strpos and substr_replace:
function sprintf2($str='', array $values = array(), $char = '?')
{
if (!$str){
return '';
}
if (count($values) > 0)
{
$len = strlen($char);
foreach ($values as $value)
{
$pos = strpos($str, $char);
if ($pos !== false) {
$str = substr_replace($str, $value, $pos, strlen($char));
}
}
}
echo $str;
}
DEMO

Answer 2

You need to escape the '?' sign in your regexp using a backslash ( '\?' instead of '?').
But your code can be easily refactored to use preg_replace_callback instead:
$params = array(1, 3);
$str = '? bla ?';
echo preg_replace_callback('#\?#', function() use (&$params) {
return array_pop($params);
}, $str);

Answer 3

Hope this code helps you.
function sprintf2($string = '', array $values = array(), $char = '?')
{
if (!$string){
return '';
}
if (count($values) > 0)
{
$exploded = explode($char, $string);
$i = 0;
$string = '';
foreach ($exploded as $segment) {
if( $i < count($values)){
$string .= ($segment . $values[$i]);
++$i;
}
}
}
echo $string;
}
$bindings = array(10, 500);
$str = "select * from `survey_interviews` where `survey_id` = ? and `call_id`= ? limit 1";
echo sprintf2($str, $bindings);
Explanation:
In your code, you're using the preg_match and the first parameter in the preg_match method is a regex pattern. what you're trying to replace is ? has a valid meaning for 0 or 1 CHARACTER. So, you've to escape that by doing \?. Though all the characters are not needed to be escaped, so, for making your method work, you've to check the character that are valid for any regex.
In my code, I've split the string for the character you want. then appending the values at the end of the part what we get from the array. and this should be done till the values length of the value array, otherwise the offset error will occur.