Question

I have noticed a strange behaviour of a str_replace function.
Can you tell me why instead of number 3 in no_2 i get no_4 ?

Here is the case:

$pattern = array(1,2,3);
$change = array(1,3,4); 
$sql = "SELECT * FROM %s WHERE no_1 IN (%s) AND no_2 IN (%s) AND no_3 IN (%s)";

$test_multiply[] = str_replace($pattern, $change, $sql);

Which gives:

Array ( [0] => SELECT * FROM %s WHERE no_1 IN (%s) AND no_4 IN (%s) AND no_4 IN (%s) ) 

Can you tell me what should I do to receive no_3 instead of no_2?

Answer 1

The documentation for str_replace() says (quoting) :

Because str_replace() replaces left to
right, it might replace a previously
inserted value when doing multiple
replacements.

I believe you are precisely in this situation :

• Your no_2 gets replaced to no_3 — because of the second item in your $pattern and $change arrays
• But, then, that no_3 gets replaced to no_4 — because of the thid item in your $pattern and $change arrays

To avoid that specific situation, you might try reversing the order of the items in those two arrays :

$pattern = array(3, 2, 1);
$change = array(4, 3, 1); 

And you’d get the following result :

SELECT * FROM %s WHERE no_1 IN (%s) AND no_3 IN (%s) AND no_4 IN (%s)