3v4l.org

run code in 300+ PHP versions simultaneously
<?php $query_string = 'foo=' . urlencode($foo) . '&bar=' . urlencode($bar); echo '<a href="mycgi?' . htmlentities($query_string) . '">'; ?>
Output for 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
Warning: Undefined variable $foo in /in/OagXo on line 2 Deprecated: urlencode(): Passing null to parameter #1 ($string) of type string is deprecated in /in/OagXo on line 2 Warning: Undefined variable $bar in /in/OagXo on line 2 Deprecated: urlencode(): Passing null to parameter #1 ($string) of type string is deprecated in /in/OagXo on line 2 <a href="mycgi?foo=&amp;bar=">
Output for 8.0.0 - 8.0.30
Warning: Undefined variable $foo in /in/OagXo on line 2 Warning: Undefined variable $bar in /in/OagXo on line 2 <a href="mycgi?foo=&amp;bar=">
Output for 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.31, 7.4.0 - 7.4.33
Notice: Undefined variable: foo in /in/OagXo on line 2 Notice: Undefined variable: bar in /in/OagXo on line 2 <a href="mycgi?foo=&amp;bar=">
Output for 7.3.32 - 7.3.33
<a href="mycgi?foo=&amp;bar=">
preferences:
269.51 ms | 401 KiB | 412 Q