1Precedence of concatenation in PHP 7 and PHP 8
2-----
3<?php
41 + 2 . 3 + 4;
51 << 2 . 3 << 4;
6-----
7!!version=8.0
8array(
9    0: Stmt_Expression(
10        expr: Expr_BinaryOp_Concat(
11            left: Expr_BinaryOp_Plus(
12                left: Scalar_Int(
13                    value: 1
14                )
15                right: Scalar_Int(
16                    value: 2
17                )
18            )
19            right: Expr_BinaryOp_Plus(
20                left: Scalar_Int(
21                    value: 3
22                )
23                right: Scalar_Int(
24                    value: 4
25                )
26            )
27        )
28    )
29    1: Stmt_Expression(
30        expr: Expr_BinaryOp_Concat(
31            left: Expr_BinaryOp_ShiftLeft(
32                left: Scalar_Int(
33                    value: 1
34                )
35                right: Scalar_Int(
36                    value: 2
37                )
38            )
39            right: Expr_BinaryOp_ShiftLeft(
40                left: Scalar_Int(
41                    value: 3
42                )
43                right: Scalar_Int(
44                    value: 4
45                )
46            )
47        )
48    )
49)
50-----
51<?php
521 + 2 . 3 + 4;
531 << 2 . 3 << 4;
54-----
55!!version=7.4
56array(
57    0: Stmt_Expression(
58        expr: Expr_BinaryOp_Plus(
59            left: Expr_BinaryOp_Concat(
60                left: Expr_BinaryOp_Plus(
61                    left: Scalar_Int(
62                        value: 1
63                    )
64                    right: Scalar_Int(
65                        value: 2
66                    )
67                )
68                right: Scalar_Int(
69                    value: 3
70                )
71            )
72            right: Scalar_Int(
73                value: 4
74            )
75        )
76    )
77    1: Stmt_Expression(
78        expr: Expr_BinaryOp_ShiftLeft(
79            left: Expr_BinaryOp_ShiftLeft(
80                left: Scalar_Int(
81                    value: 1
82                )
83                right: Expr_BinaryOp_Concat(
84                    left: Scalar_Int(
85                        value: 2
86                    )
87                    right: Scalar_Int(
88                        value: 3
89                    )
90                )
91            )
92            right: Scalar_Int(
93                value: 4
94            )
95        )
96    )
97)
98