Why is the result of sorting arrays by sort = 1?

Why is the result of sorting arrays by sort = 1 PHPcode $ a = array (,); $ a = sort ($ a); print_r ($ ); result: 1. I cannot explain it! Solving !!!, 1 indicates that the sorting is successful. PHPcode $ a = why is the result of sorting arrays by sort = 1?

PHP code

  $ A = array (2, 4, 3, 7, 5); $ a = sort ($ a); print_r ($ );

Result: 1;
Think twice! Solution !!!

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1 indicates that the sorting is successful.

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PHP code

$ A = array (2, 4, 3, 7, 5); echo sort ($ a); print_r ($ );
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Sort () is obtained from the ground, and the returned result is successful. true = 1, so you should output $