A brief discussion on PHP source code twenty-four: Analysis of the reasons why iteration cannot be completed when the value is false in iterator implementation

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There is an article in the previous article about the simple implementation of iterator and the Yii framework There is a simple iterator implementation in the iterator implementation. There is a problem left here. When the iteration value contains false, the foreach loop ends at this place. What is the reason?

Follow Brother Bird’s idea and find relevant clues at line 8131 of the Zend/zend_vm_execute.h file, as shown below:

 /*  */
 if (!iter || (iter->index > 0 && iter->funcs->valid(iter TSRMLS_CC) == FAILURE)) {
 /* reached end of iteration */
 if (EG(exception)) {
 array->refcount--;zval_ptr_dtor(&array);ZEND_VM_NEXT_OPCODE();}
 ZEND_VM_JMP(EX(op_array)->opcodes+opline->op2.u.opline_num);}

For the simple iterator implemented, iter->funcs- >valid(iter TSRMLS_CC) method calls the valid() method,

If our value is false, the value returned through current is false, and when accessed through foreach, the traversal is interrupted here. , the program will continue to execute the following code instead of this loop

Solution

Process the key and value in the array separately

In the valid(), rewind(), next() methods Operate key in instead of value
Only return value in current
Such as the simple implementation of the iterator in the article and the implementation of the iterator in the Yii framework and the implementation of CMapIterator in the Yii framework

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