Collocations and phrasal verbs are identical phenomena, since both consist only of a fixed combination of a verb and a preposition. 

Collocations are random word combinations with no usage pattern, whereas phrasal verbs have meanings that are fully predictable from their individual parts. 

Collocations refer to the natural association between a key word and other words that frequently occur with it, whereas phrasal verbs are combinations of a verb plus a particle whose meaning may vary depending on the words they combine with. 

Phrasal verbs can only be understood when used in isolation, while collocations always depend on complex grammatical context.