Memory exhausted error for json_parse with PHP
THIS IS A VERY BAD IDEA, that said, you'll need to set
ini_set('memory_limit',filesize($FILE) + SOME_OVERHEAD_AMOUNT);because you're reading the entire thing into memory. You may very well have to set the memory limit to two times the size of the file since you also want to JSON_DECODE
NOTE THAT ON A WEB SERVER THIS WILL CONSUME MASSIVE AMOUNTS OF MEMORY AND YOU SHOULD NOT DO THIS IF THE FILE WILL BE MANY GIGABYTES AS YOU SAID!!!!
Is it really a giant JSON blob? You should look at converting this to a database or other format which you can use random or row access with before parsing with PHP.