- substr: documentation ( source)
- strpos: documentation ( source)
<?php
$agent_name = 'aperry@clickspark.com';
$agent_name2 = 'crobinson';
$agent_name = strpos($agent_name, '@') === false ? $agent_name : substr($agent_name, 0, strpos($agent_name, '@'));
$agent_name2 = strpos($agent_name2, '@') === false ? $agent_name2 : substr($agent_name2, 0, strpos($agent_name2, '@'));
echo $agent_name.PHP_EOL.$agent_name2;