PHP add text to string at certain positions -issue

Question

I'm trying to insert text to string at certain positions (before letter "b" in this case), but for some reason the code I have only insert text (" test ")at the last position/occurance.

<?php
$str = "aabaaaaabaaaaab";
$needle = "b";
$teststr = " test ";
$lastPos = 0;
$positions = array();


while (($lastPos = strpos($str, $needle, $lastPos))!== false) {
$positions[] = $lastPos;
$lastPos = $lastPos + strlen($needle);
}

for ($i=0;$i<count($positions);$i++) {
$newstring = substr_replace($str,$teststr,$positions[$i],0);
}

echo $newstring;
?>`

this produces the following output: aabaaaaabaaaaa test b when the desired one whould be: aa test aaaaa test aaaaa test b

jh1711 · Accepted Answer · 2018-01-14 16:17:15Z

1

You use $str as input for substring_replace, but you don't modify $str anywhere. Obviously only the last replacement will show. You can, for example, use $newstring as input for substring_replace, but then you positions are no longer correct. This can be avoided by making the replacements from right to left:

//snip

$newstring = $str;
for ($i = count($positions) - 1; $i >= 0; $i--) {
  $newstring = substr_replace($newstring, $teststr, $positions[$i], 0);
}

echo $newstring;

answered Jan 14, 2018 at 16:17

jh1711

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1 Comment

Micke Over a year ago

Thanks a lot! I have been banging my head against the wall with this issue for hours now!

Raul Sauco · Accepted Answer · 2018-01-14 16:05:49Z

0

Would regular expressions work for you?

<?php
$str = "aabaaaaabaaaaab";
echo preg_replace('~b~', ' test b', $str);

answered Jan 14, 2018 at 16:05

Raul Sauco

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1 Comment

Micke Over a year ago

It probably would, but I try to avoid regex at all cost. Thanks for your input though.

bitto kazi · Accepted Answer · 2018-01-14 16:11:50Z

0

$str = "aabaaaaabaaaaab";
$needle = "b";
$teststr = " test ";
$lastPos = 0;
$positions = explode($needle, $str);
foreach($positions as $k=>$v) {
    $positions[$k]=$v.$teststr.$needle;
}
$positions=implode($positions);
echo $positions;

Try This

answered Jan 14, 2018 at 16:11

bitto kazi

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1 Comment

Micke Over a year ago

Thanks mate, I tried this code also, but I found that it adds a additional "test b" in the end. Ie. the result is: aa test baaaaa test baaaaa test b test b.

Mahesh Hegde · Accepted Answer · 2018-01-14 16:29:25Z

0

Following should work

$str = "aabaaaaabaaaaab";
$needle = "b";
$teststr = " test ";

for ($i=0;$i<strlen($str);$i++) {
    if($str[$i]==$needle ){
        echo $teststr.$str[$i]; 
    }else{
        echo $str[$i];
    }
}

echo $newstring;

**Output** 
aa test baaaaa test baaaaa test b

answered Jan 14, 2018 at 16:29

Mahesh Hegde

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