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