Can you append strings to variables in PHP?

Question

Why does the following code output 0?

It works with numbers instead of strings just fine. I have similar code in JavaScript that also works. Does PHP not like += with strings?

<?php
    $selectBox = '<select name="number">';
    for ($i=1; $i<=100; $i++)
    {
        $selectBox += '<option value="' . $i . '">' . $i . '</option>';
    }
    $selectBox += '</select>';

    echo $selectBox;
?>

Solution 1

This is because PHP uses the period character . for string concatenation, not the plus character +. Therefore to append to a string you want to use the .= operator:

for ($i=1;$i<=100;$i++)
{
    $selectBox .= '<option value="' . $i . '">' . $i . '</option>';
}
$selectBox .= '</select>';

Solution 2

In PHP use .= to append strings, and not +=.

Why does this output 0? [...] Does PHP not like += with strings?

+= is an arithmetic operator to add a number to another number. Using that operator with strings leads to an automatic type conversion. In the OP's case the strings have been converted to integers of the value 0.

---

More about operators in PHP:

• Reference - What does this symbol mean in PHP?
• PHP Manual – Operators

Solution 3

PHP syntax is little different in case of concatenation from JavaScript. Instead of (+) plus a (.) period is used for string concatenation.

<?php

$selectBox = '<select name="number">';
for ($i=1;$i<=100;$i++)
{
    $selectBox += '<option value="' . $i . '">' . $i . '</option>'; // <-- (Wrong) Replace + with .
    $selectBox .= '<option value="' . $i . '">' . $i . '</option>'; // <-- (Correct) Here + is replaced .
}
$selectBox += '</select>'; // <-- (Wrong) Replace + with .
$selectBox .= '</select>'; // <-- (Correct) Here + is replaced .
echo $selectBox;

?>

Comments

[Charles Sprayberry]

Reference for PHP operators

[Henrik]

Is this question really a duplicate? The question asks for appending a string in a special case with a further more specific question about the output of the code.

[John]

$selectBox = '<select>'; $selectBox += '</select>'; Expands to $selectBox = '<select>' + '</select>'; PHP converts strings to 0 if they don't at least begin with numbers. Hence 0+0