Imagick::setResourceLimit

IMagick::RESOURCETYPE_THREADS is missing, yet you're still able to limit the number of thready ImageMagick should use:

<?php
// IMagick::setResourceLimit(IMagick::RESOURCETYPE_THREADS, 2);
IMagick::setResourceLimit(6, 2);

Note that the limits are given in bytes instead of megabytes. You can verify with:

<?php echo Imagick::getResourceLimit(Imagick::RESOURCETYPE_MEMORY); ?>

This list should help setting the limits:

imagick::RESOURCETYPE_AREA (integer)   //equivalent of MAGICK_AREA_LIMIT
imagick::RESOURCETYPE_DISK (integer)   //equivalent of MAGICK_DISK_LIMIT
imagick::RESOURCETYPE_FILE (integer)   //equivalent of MAGICK_FILE_LIMIT
imagick::RESOURCETYPE_MAP (integer)    //equivalent of MAGICK_MAP_LIMIT
imagick::RESOURCETYPE_MEMORY (integer) //equivalent of MAGICK_MEMORY_LIMIT

Here are the RESOURCETYPE actually supported by today:
https://github.com/Imagick/imagick/blob/master/imagick_helpers.c
https://github.com/Imagick/imagick/blob/master/ChangeLog

Added in 3.3:
* Imagick::RESOURCETYPE_TIME
* Imagick::RESOURCETYPE_THROTTLE

Added in 3.2:
* Imagick::RESOURCETYPE_THREAD

Note that Imagick::setResourceLimit may return success without actually changing the limits (verify with Imagick::getResourceLimit). This is at least true for Imagick::RESOURCETYPE_WIDTH and Imagick::RESOURCETYPE_HEIGHT, where values exceeding the limits defined in policy.xml are silently ignored.