Allowed memory size of 33554432 bytes exhausted

Question

I have a little problem when I try to run my application, because then I have an application made with Doctrine + php and from time to time began to give that error follows:

PHP Fatal error:  Allowed memory size of 33554432 bytes exhausted 
(tried to allocate 8388608 bytes) 
 in /home/mentorsitescom/public_html/prefeituraexemplo/mpe-serv-sol-desenv/vendor/doctrine/annotations/lib/Doctrine/Common/Annotations/DocParser.php on line 236

I’ve tried setting via php the memory limit to:

ini_set('memory_limit', '2048M');

or to

ini_set('memory_limit', '-1');

Only that still the mistake continues, someone can help me