Editing PHP Skills Tests (section)

=== String concatenation and string operators ===

<syntaxhighlight lang="php">
echo (2).(3*(print 3)); // "323"
</syntaxhighlight>

* This example also plays on the obscure fact that the `print` construct always returns the value `1`. 
* `echo` evaluates everything to the right.
* First, `print 3` outputs `"3"`.
* Then 3 is multiplied by the return value of `print`, i.e. `1`, for a result of `3`;
* `2` is concatenated to `3` for `"23"`
* `echo` outputs `"23"` after the `"3"` that has already been output, for a result of `"323"`.


----

'''Q: What will be the output of the following code?'''

<syntaxhighlight lang="php">
$foo = 5 + "10 things";
print $foo; // 15
</syntaxhighlight>

{|
! a.
| 510 things
|-
! b.
| 5 10 things
|-
! c.
| 15 things
|-
! d.
| 15
|-
! e.
| None of the above
|}

'''A: (d) 15'''

* One trick to this question is that there is no string concatenation operator (`.`) involved.
* Still one thing to keep in mind is that the dot operator has the same precedence as `+` and `-`.
* Non-empty non-numeric strings are converted to `0` when they are part of a mathematical operation. <ref>[http://php.net/manual/en/language.operators.string.php String Operators], PHP documenation</ref>
* But a string is numeric if the numeric part comes at the beginning.
** `"10 things" = 10`
** `"things 10" = 0`
** `"10things" = 10`
** `"10 x 4" = 10` 
* `"10 things"` is converted to `10`, then added to `5`.
* The final result is `15`.