I need to replace multiple value using str_replace.
This is my PHP code fore replace.
$date = str_replace(
array('y', 'm', 'd', 'h', 'i', 's'),
array('Year', 'Month', 'Days', 'Hours', 'Munites', 'Seconds'),
$key
);
When i pass m in $key it return output like.
MontHours
When i pass h in $key it return output.
HourSeconds
it return this value i want the Month only.
This is a replacement gotcha which is mentioned in the documentation for str_replace():
Replacement order gotcha
Because
str_replace()replaces left to right, it might replace a previously inserted value when doing multiple replacements. See also the examples in this document.
Your code is equivalent to:
$key = 'm';
$key = str_replace('y', 'Year', $key);
$key = str_replace('m', 'Month', $key);
$key = str_replace('d', 'Days', $key);
$key = str_replace('h', 'Hours', $key);
$key = str_replace('i', 'Munites', $key);
$key = str_replace('s', 'Seconds', $key);
echo $key;
As you can see m gets replaced with Month, and h in Month gets replaced with Hours and the s in Hours gets replaced with Seconds. The problem is that when you're replacing h in Month, you're doing it regardless of whether the string Month represents what was originally Month or what was originally an m. Each str_replace() is discarding some information — what the original string was.
This is how you got that result:
0) y -> Year
Replacement: none
1) m -> Month
Replacement: m -> Month
2) d -> Days
Replacement: none
3) h -> Hours
Replacement: Month -> MontHours
4) i -> Munites
Replacement: none
5) s -> Seconds
Replacement: MontHours -> MontHourSeconds
The solution would be to use strtr() because it won't change already replaced characters.
$key = 'm';
$search = array('y', 'm', 'd', 'h', 'i', 's');
$replace = array('Year', 'Month', 'Days', 'Hours', 'Munites', 'Seconds');
$replacePairs = array_combine($search, $replace);
echo strtr($key, $replacePairs); // => Month
From the manual page for str_replace():
Caution
Replacement order gotcha
Because str_replace() replaces left to right, it might replace a previously inserted value when doing multiple replacements. See also the examples in this document.
For example, "m" is replaced with "Month", then the "h" in "Month" is replaced with "Hours", which comes later in the array of replacements.
strtr() doesn't have this issue because it tries all keys of the same length at the same time:
$date = strtr($key, array(
'y' => 'Year',
'm' => 'Month',
'd' => 'Days',
'h' => 'Hours',
'i' => 'Munites', // [sic]
's' => 'Seconds',
));
A simpler fix is to change the search order:
array('Year', 'Seconds', 'Hours', 'Month', 'Days', 'Minutes')
str_replace and preg_replace will both search for each search item one at a time. Any multi-value will need to make sure the order doesn't change a previous replace item.
