Description:
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Replacing items in an array of  20-30 items with str_replace seems to leak memory. The application in question would crash when parsing various larger CSV files, using upwards to >500MB  per an 18MB data-file. 

Jumps in memory usage were observed at the point where str_replace was run. Using the function 'preg_replace' instead issued no such leak

Reproduce code:
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str_replace('~comma~', ',', $myarray );

Expected result:
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(values of ~comma~ in string were replaced with actual commas)

Actual result:
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Progress would end indicating in logs that the memory limit of 500MB (as indicated in php.ini) was exceeded.