Description:
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When extending internal class which has defined static property with null value and accessing this static property in C code using zend_read_static_property there is value returned as &NULL in C code causing some comparisons to fail. Though value in php code of this static property is correctly returned as NULL.

This also happens for php 7.1 as well.

Test script:
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In class init:

zend_declare_property_null(test3_test_ce, sizeof("someNull")-1, ZEND_ACC_PUBLIC|ZEND_ACC_STATIC TSRMLS_CC);

Access and dump it somwhere(keep in mind you must extends class in php first):

zval *tmp = zend_read_static_property(ce, sizeof("someNull")-1, len, (zend_bool) ZEND_FETCH_CLASS_SILENT); // here will be returned &NULL
php_var_dump(tmp, 1); // var dumps &NULL
if (Z_TYPE_P(tmp) == IS_NULL) // false