Although i was also confuse since both look too similar interms of the design and colour combination - But the fact is the below image
In the above you can see the difference between the Pakistani flag and Islamic flag
More information about the Islamic flag :
This above green Islamic flag with crescent and star became a standard Islamic flag and is used till date, and another interesting point on the above islamic flag is that it is been used by Muslim since the establishment of this flag.
Used by some variations in the original Islamic Flag :
Some use variations in the crescent flag in many countries such as Pakistan as an example with white strip. other countries who use variation in the Islamic flag with the images below
Below is the image where tweeple think that the flag is a Pakistani flag