ループ本体内で array_push() を使用しないでください。

$a = []; array_push($a,'test');
$a[] = 'test';

ArrayPush
一个 ArrayPush 类
pushEachOne() 循环体中使用 array_push() 来为 $a 追加元素
pushEachTwo() 循环体中使用 $a[] = $var 来为 $a 追加元素
/**
 * Class ArrayPush
 */
class ArrayPush
{
    /**
     * @param int $times
     * @return array
     */
    public static function pushEachOne(int $times): array
    {
        $a = [];
        $b = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
        for ($i = 0; $i < $times; $i++) {
            array_push($a, $b[$i % 10]);
        }
        return $a;
    }
    /**
     * @param int $times
     * @return array
     */
    public static function pushEachTwo(int $times): array
    {
        $a = [];
        $b = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
        for ($i = 0; $i < $times; $i++) {
            $a[] = $b[$i % 10];
        }
        return $a;
    }
}

ini_set('memory_limit', '4000M');
$timeOne = microtime(true);
$a       = ArrayPush::pushEachOne(1000000);
echo 'count pushEachOne result | ' . count($a) . PHP_EOL;
$timeTwo = microtime(true);
$b       = ArrayPush::pushEachTwo(1000000);
echo 'count pushEachTwo result | ' . count($b) . PHP_EOL;
$timeThree = microtime(true);
echo PHP_EOL;
echo 'pushEachOne | ' . ($timeTwo - $timeOne) . PHP_EOL;
echo 'pushEachTwo | ' . ($timeThree - $timeTwo) . PHP_EOL;
echo PHP_EOL;

count pushEachOne result | 1000000
count pushEachTwo result | 1000000
pushEachOne | 1.757071018219
pushEachTwo | 0.67165303230286

array_push — 将一个或多个单元压入数组的末尾（入栈）
array_push ( array &$array , mixed $value1 [, mixed $... ] ) : int
array_push() 将 array 当成一个栈，并将传入的变量压入 array 的末尾。array 的长度将根据入栈变量的数目增加。和如下效果相同：
<?php$array[] = $var;?>

/* {{{ proto int array_push(array stack, mixed var [, mixed ...])
   Pushes elements onto the end of the array */
PHP_FUNCTION(array_push)
{
    zval   *args,       /* Function arguments array */
           *stack,      /* Input array */
            new_var;    /* Variable to be pushed */
    int i,              /* Loop counter */
        argc;           /* Number of function arguments */
    //这一段是函数的参数解析
    ZEND_PARSE_PARAMETERS_START(2, -1)
        Z_PARAM_ARRAY_EX(stack, 0, 1)
        Z_PARAM_VARIADIC('+', args, argc)
    ZEND_PARSE_PARAMETERS_END();
    /* For each subsequent argument, make it a reference, increase refcount, and add it to the end of the array */
    for (i = 0; i < argc; i++) {
        //拷贝一个
        ZVAL_COPY(&new_var, &args[i]);
        //插入新数值，自动
        if (zend_hash_next_index_insert(Z_ARRVAL_P(stack), &new_var) == NULL) {
            if (Z_REFCOUNTED(new_var)) Z_DELREF(new_var);
            php_error_docref(NULL, E_WARNING, "Cannot add element to the array as the next element is already occupied");
            RETURN_FALSE;
        }
    }
    /* Clean up and return the number of values in the stack */
    RETVAL_LONG(zend_hash_num_elements(Z_ARRVAL_P(stack)));
}
/* }}} */

ZEND_API int add_next_index_long(zval *arg, zend_long n) /* {{{ */
{
    zval tmp;
    ZVAL_LONG(&tmp, n);
    return zend_hash_next_index_insert(Z_ARRVAL_P(arg), &tmp) ? SUCCESS : FAILURE;
}
/* }}} */
ZEND_API int add_next_index_null(zval *arg) /* {{{ */
{
    zval tmp;
    ZVAL_NULL(&tmp);
    return zend_hash_next_index_insert(Z_ARRVAL_P(arg), &tmp) ? SUCCESS : FAILURE;
}
/* }}} */
ZEND_API int add_next_index_bool(zval *arg, int b) /* {{{ */
{
    zval tmp;
    ZVAL_BOOL(&tmp, b);
    return zend_hash_next_index_insert(Z_ARRVAL_P(arg), &tmp) ? SUCCESS : FAILURE;
}
/* }}} */
ZEND_API int add_next_index_resource(zval *arg, zend_resource *r) /* {{{ */
{
    zval tmp;
    ZVAL_RES(&tmp, r);
    return zend_hash_next_index_insert(Z_ARRVAL_P(arg), &tmp) ? SUCCESS : FAILURE;
}
/* }}} */
ZEND_API int add_next_index_double(zval *arg, double d) /* {{{ */
{
    zval tmp;
    ZVAL_DOUBLE(&tmp, d);
    return zend_hash_next_index_insert(Z_ARRVAL_P(arg), &tmp) ? SUCCESS : FAILURE;
}
/* }}} */
ZEND_API int add_next_index_str(zval *arg, zend_string *str) /* {{{ */
{
    zval tmp;
    ZVAL_STR(&tmp, str);
    return zend_hash_next_index_insert(Z_ARRVAL_P(arg), &tmp) ? SUCCESS : FAILURE;
}
/* }}} */
ZEND_API int add_next_index_string(zval *arg, const char *str) /* {{{ */
{
    zval tmp;
    ZVAL_STRING(&tmp, str);
    return zend_hash_next_index_insert(Z_ARRVAL_P(arg), &tmp) ? SUCCESS : FAILURE;
}
/* }}} */
ZEND_API int add_next_index_stringl(zval *arg, const char *str, size_t length) /* {{{ */
{
    zval tmp;
    ZVAL_STRINGL(&tmp, str, length);
    return zend_hash_next_index_insert(Z_ARRVAL_P(arg), &tmp) ? SUCCESS : FAILURE;
}
/* }}} */
ZEND_API int add_next_index_zval(zval *arg, zval *value) /* {{{ */
{
    return zend_hash_next_index_insert(Z_ARRVAL_P(arg), value) ? SUCCESS : FAILURE;
}
/* }}} */