Go deep into the foreach loop and the unset () function.

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Foreach ($ arr as $ key => $ val) {if (in_array ($ val, $ pattern) {unset ($ arr [$ key]); break ;}} foreach ($ arr as $ key => $ val) {if (in_array ($ val, $ pattern) {unset ($ val); break ;}} pasted some code, I want to know why the unset () function is unset ($ arr [$ key]) instead of unset ($ val ).

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Foreach ($ arr as $ key => $ val) {if (in_array ($ val, $ pattern) {unset ($ arr [$ key]); break ;}} foreach ($ arr as $ key => $ val) {if (in_array ($ val, $ pattern) {unset ($ val); break ;}} pasted some code, I want to know why the unset () function is unset ($ arr [$ key]) instead of unset ($ val ).

Let me briefly explain the differences:

Unset ($ arr [$ key]) // destroys an element in the $ arr array.

Unset ($ val) // The $ val variable when it is destroyed. this variable is an element in $ arr, which is equivalent to re-opening a variable, destroying this re-opened variable will not affect the original array $ arr.

Do you have any questions?

Foreach ($ arr as $ key => $ value) {$ key and $ value // A brand new variable for reinitialization, regardless of $ arr}